Technical Field
This invention relates to a gripping device for handling reinforcement cages for tower segments of a wind turbine.
Description of the Related Art
Towers of the kind used for wind turbines, amongst other things, often have a wall made of concrete or reinforced concrete. Especially in the case of towers that are subject to dynamic forces, which applies to most towers due to the wind, additional strengthening structures called reinforcement cages are used on the inside of the tower wall to improve stability. Such towers have a segmented design, i.e., a tower is built with several, essentially ring-shaped tower segments placed on top of each other.
At this point, the following documents are generally pointed out as prior art: DE 29 29 035 C2, DE 295 16 996 U1, DE 20 2010 008 450 U1, U.S. Pat. No. 5,306,062A and U.S. Pat. No. 1,810,583A.
During the manufacturing of such tower segments, first of all the reinforcement cage is manufactured and then it is surrounded by concrete filled into purpose-designed molds and cured.
Known apparatus for manufacturing reinforcement cages for tower segments requires a supporting structure, which holds numerous rods called rakes. These rods respectively have holding fixtures for holding steel cables, wherein the steel cables are arranged around the supporting structure in order to form ring elements. Stabilized by the rods, these ring elements are connected with steel elements that are orthogonal to them and preformed in an arched shape, through which a grate-shaped reinforcement cage is created. The reinforcement cables are either wrapped around a stationary supporting structure, or, preferably, are located in a stationary feeding device and are pulled out of the rotatory holding fixture by the supporting structure and, due to the rotational movement of the supporting structure, are arranged in rings around the supporting structure. The shape of the ring-shaped steel cables is stabilized throughout by the supporting structure and the rods by numerous spokes extending between the supporting structure and the rods. In known systems, in order to remove the reinforcement cages from the apparatus the spokes must either be detached or the stabilizing rods have to be unhooked from the steel cables individually and manually.
Depending on the size of the tower segments to be manufactured, even the reinforcement cages are of considerable weight and, depending on the tower segment, considerable size. A reinforcement cage for the lowest, i.e., the largest tower segment of a type E126 wind turbine from ENERCON, for example, has a diameter of around 14 m, a height of around 3.7 m and a weight of around 8.5 t. Due to their grate-like structure and enormous size, it is very hard to handle the reinforcement cages with conventional crane systems during production.